The present proposal aims to evaluate outcome in adulthood of clients with autism who received intensive behavioral treatment as children. Autism is a severely handicapping condition with onset in early childhood. Most persons with autism reqUire lifelong supervised or institutional care. They exhibit deviant and/or delayed development in intellectual, social, emotional, and self-help skills, often accompanied by high rates of aggressive, self-injurious, and ritualistic behaviors. Several recent studies have reported favorable outcome of early and intensive behavioral intervention in autism. Of these studies, the Lovaas (1987) study has had the most comprehensive intervention and long-term follow-up. Clients (mean IQ=60; mean CA=34 months) were assigned to an experimental group (n=19) or to a minimal treatment control group (n=19). Nineteen pre-treatment variables showed the groups to be similar to each other and to other groups of preschool children with autism. The experimental group received an intensive, in-home behavioral treatment for 2 or more years. The control group received minimal behavioral treatment (10 hours a week or less). Follow-up l at CA=7 years showed that the experimental group had achieved a less restrictive school placement and higher 10 scores than the control group (mean 10=83 vs. 10=52, respectively). Follow-up II at mean CA=11.5 years showed that the experimental group subjects had preserved their gains while control group subjects showed no change. An extensive, double-blind evaluation of the 9 best outcome experimental subjects showed 8 of them to be indistinguishable from average children on commonly used and well-normed tests of intellectual, social and emotional functioning. Subjects in this study are now adults aged 19-29 years. Consequently, they have experienced many new social, emotional and intellectual demands. Study 1 will evaluate the overall effectiveness of intensive and early intervention by comparing experimental and control group subjects on tests of intellectual and educational achievement, social and emotional functioning, occupational status, adaptive skills, diagnosis, and presence of clinically acute problems such as the extent of self-injury and assaultive behaviors, medication, rate and kind of institutionalization, and cost of treatment. Study 2 will consist of a particularly rigorous evaluation of the 9 best-outcome subjects identified in Follow-up l. The evaluation will focus on residual problems and subtle signs of autism such as thought and language disturbances, affective flattening, social awkwardness, difficulties in pragmatics, and socially significant indicators of quality of life, including work, marriage and parenthood. Data from Study 1 and 2 will contribute information about the strengths and weaknesses of intensive and early behavioral intervention, thereby providing direction for improvement in future treatments. Implications for theories of autism will also be identified.